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Correlation between cumulative labeling indices measured in the terminal bronchioles and in the centriacinar region in the lungs of rats exposed to oxidant air pollutants.

A study was conducted to the determine how alterations in the terminal bronchioles may reflect alterations in the centriacinar region induced by exposure to air pollutants such as ozone (10028156) (O3) and nitrogen-dioxide (10102440) (NO2). Twenty healthy male Sprague-Dawley-rats were separated into four experimental groups, one of which served as a control. Groups two, three, and four were exposed in chambers to 0.6 part per million (ppm) O3, 10.8ppm NO2, or 0.6ppm O3 and 10.8ppm NO2, respectively, for 8 hours a night, on 7 consecutive days. Following exposure, the rats were killed and the lungs were removed for tissue preparation and analysis. Labeling indices were measured in the epithelium of the terminal bronchioles and the centriacinar regions. The lungs of the rats exposed to NO2 or NO2 and O3 had significantly lower labeling indices in the centriacinar region than in the terminal bronchioles, while the lungs of controls and O3 exposed rats had the same labeling indices in the two regions. A highly significant correlation between the labeling index in the terminal bronchioles and the labeling index in the adjacent centriacinar zone was observed. The authors conclude that the labeling index in the terminal bronchioles can be a sensitive indicator for lung injury caused by O3 exposure.